Overhead valve internal combustion engines include a cylinder block portion and a cylinder head which are bolted together. The cylinder block includes at least one cylinder bore opening to an end face and a push rod cavity spaced from and generally parallel to the cylinder bore and opening to the end face of the cylinder block. The cylinder head includes a corresponding number of combustion chambers forming the top of the cylinder bores, at least one intake valve and exhaust valve allowing communication of each combustion chamber with intake and exhaust ports, respectively, valve springs, rocker arms, and a push rod cavity. The combustion chamber and push rod cavity of the cylinder head open to an end face in alignment with their counterparts in the cylinder block. A gasket is provided between the end faces of the cylinder block and the cylinder head to seal the interface therebetween.
In some engine designs, the push rod cavity is a large rectangular cavity that houses multiple overhead valve push rods. In designs utilizing multiple intake and exhaust valves per cylinder, a single push rod is generally used to actuate multiple valves. Thus, each cylinder bore typically is associated with two push rods, one each to actuate intake and exhaust valves. In engines having up to four cylinder bores per cylinder block and head, such as in V-8 engines, the rectangular push rod cavity must be large enough to house up to eight push rods in close relation to the chambers.
In such engines, assembly of the cylinder block and cylinder head may be problematic due to the push rod locations within the push rod cavity. In a typical assembly, the push rods are inserted into the cylinder block after attaching the cylinder head thereto, and are allowed to "float" within the push rod cavity until later attachment to rocker arm assemblies. After head attachment, the push rod must then be aligned and interconnected with the rocker arm assemblies attached to the cylinder head, as well as to the cam following of the camshaft, typically requiring extra assembly time. However, in overhead valve internal combustion engines, the rocker arm of the valve mechanism is located at a relatively great distance from the cam shaft, requiring a relatively long push rod connecting the cam of the cam shaft to the rocker arm of the valve lifter. Since each push rod may be on the order of one and one-half feet long, alignment of the push rods during assembly may be difficult, requiring extra manufacture time and effort, thereby increasing assembly difficulty and cost.
However, as noted above, a gasket is provided between the end faces of the cylinder block and the cylinder head to seal the interface therebetween. The gasket includes a rectangularly shaped cutout to surround the push rod cavity. It is known to provide discrete holes through a gasket sized and shaped to receive individual push rods, or to support the push rod from laterally deflecting during reciprocation thereof by providing tabs that extend into the push rod cavity hole and also extend upwardly out of the gasket plane. However, use of individual holes is not practical for engines having a relatively large rectangular push rod cavity, since the cavity allows lubricant to flow from the engine head to the camshaft, push rod cam follower, and camshaft bearings. Moreover, in larger multi-cylinder engines, push rod lateral deflection is minimized by increasing the size of the push rod itself. Additionally, in known designs supporting the push rod, only lateral movement of the push rods perpendicular to the rocking plane of the rocker arms is restricted while lateral movement of the push rods in the rocking plane of the rocker arms incidental to the rocking motion of the rocker arms is permitted. Since only partial lateral support is provided to the push rod, and only during push rod reciprocation during engine operation, the design does not assist in locating the push rod for assembly, and instead allows significant movement of an unsecured push rod prior to assembly. It is therefore desirable to incorporate features onto the gasket that assist in locating and retaining the push rods prior to engine assembly to simplify the assembly of the cylinder head to the cylinder block, while still allowing the push rods to be retained within a large, rectangular cavity.